Irreproducible Results in Thompson et al. (2006)

J. Huston McCulloch,
"Irreproducible results in Thompson et al., 'Abrupt Tropical Climate Change: Past and Present' (PNAS 2006)."
Energy & Environment Vol. 20, No. 3 (2009), pp. 367-73.
PDF of published article.

Supplementary Data File as used by JHM
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Discussion on Climate Audit


Lonnie G. Thompson et al.,
"Abrupt Tropical Climate Change: Past and Present."
Proceedings of the National Academy of Sciences, USA 103 (July 11): 10536-10543.
PDF

Supporting data sets as posted on PNAS website
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Further results

Adapted from a comment posted May 1, 2009 on Climate Audit.

Since my EE note has come out, I have tried some additional calculations with the PNAS06 data that have localized the inconsistency between Data Sets 2 and 3.

It turns out that the root of the problem is that the decadal average Z-scores shown in Thompson's Figure 6 and my Figure 1 above, and tabulated back to year 0 in Data Set 3, are not the decadal averages of the 5-year average Z-scores shown back to 1600 in Thompson et al.'s Figure 5 and in their Data Set 2:


Evidently different data was used for Figure 6 (which Thompson et al. compare approvingly to the Mann et al. 1999 Hockey Stick) than for Figure 5, even though the article and SI give no indication that this was the case.

The problem is not isolated to the data for just one region, since the two regional indices have the same problem:

I found that the Data Set 2 composite scores really can be constructed as linear combinations of the Data Set 2 core data, with all coefficients for the appropriate regions highly significant as if from an exact fit to within rounding error. The included coefficients are similar but unequal, as if z-scores were computed from the d18O data and then averaged for each region.

However, the problem cannot just be that Figure 6 was computed from the same data but using standard errors for the 2000-year period instead of the 400-year period of Figure 5, since then there would still be an exact (though different) linear relation between the Figure 6 composites and decadal averages of the Figure 5 core data. As I show in my EE paper, no such linear relation exists.

So the problem still persists which is the right data to use to construct an ice core temperature proxy? The data of Figure 5 (which although it only goes back to 1600 AD is at least identified by core number in DS2), or the (unspecified) data used to construct Figure 6?

Since Figure 5 is not representative of the data that was used to construct Figure 6, Thompson and co-authors have failed to provide, as required by the PNAS data policy, sufficient data to replicate his results. At a minimum they should identify the archived cores that were used to construct Figure 6, and provide detailed data for any unarchived cores that were used.

Added 5/11/09


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